Additional information about the side effects of radiotherapy
Because a human body is a delicate and complicated biological system, and the inter-communication among different organs are even more complex, some side effects are inter-connected and may not be clearly separated from one another. Let’s use some examples for further illustration.
Cancer patients treated by high dose radiation onto specific organ may suffer organ damages in addition to other side effects (hair loss, diarrhea, etc.). Let’s look at the radiotherapy on liver cancer as a specific example. Patients with liver cancer, when treated by ionizing radiation, may suffer from liver damage and/or liver function reduction.
There are
several reasons why organ damages occur after radiation therapy. The obvious
reason is that liver cells damaged by DNA will result in the damage of liver
tissue through mechanisms such as programmed cell death (apoptosis). The other
important reason is that certain cytokines, such as TNF-a, in liver and
blood are often markedly induced by radiation therapy. As described before,
abnormally elevated levels of TNF-a will kill
the surrounding cells (no matter cancer cells or normal cells), and will cause
certain liver damage.
Our experimental results showed that radiation in
mouse liver induced liver damage (reflected by elevated serum levels of both
aspartate transaminase (AST) and alanine transaminase (ALT), and the liver
damage is in correlation with increased levels for serum TNF-a induced by irradiation. Pre-treatment of mice with a small-molecule TNF-a modulator UTL-5d (Fig. 2.2) effectively reduced
TNF-a secretion and resulted in marked reduction of
ALT/AST levels. This implies that TNF-a may play an important role in damaging the liver
and UTL-5d compound may be a potential agent for radioprotection.
Fig. 2.2 Structure of UTL-5d
In order to reduce the side effects induced by radiotherapy, there are several general strategies being employed as described in the next chapter.